1. Field of the Invention
The present invention relates to a device for the production of at least two adjacent perforation rows in cigarettes and/or filter-lining paper or filter-wrapping paper, using a laser light source.
2. Description of the Prior Art
In connection with the introduction of ventilated cigarettes a number of different methods have been developed for the production of the perforation zones which consist of a row of ventilation holes and/or slots.
In practise, basically two methods are used, i.e. the electrostatic perforation or the perforation with a pulsed or focused laser beam. Either the wrapping materials, that is the filter-lining paper or filter-wrapping paper, or the finished cigarettes are perforated.
The wrapping materials are perforated either on separate machines which are not integrated into the procedure of a production installation (off-line), or during the production of the cigarettes themselves (on-line).
Finished double-length filter cigarettes are perforated during production, i.e. on-line, in that either the individual holes are produced consecutively by means of one laser pulse each or all of the holes of the cigarette are produced simultaneously by one laser pulse each. Thus, for each individual cigarette a single row of successive perforations is produced. In the case of a pulsed laser the cigarette has to be rotated by 360.degree. about its longitudinal axis. For this purpose solutions are known, some of which require a great deal of time and effort.
One or several rows of perforation zones can be produced in the wrapping materials, i.e. the filter-lining or filter-wrapping paper. Moreover, it is known for finished individual cigarettes to provide by means of pulsed laser double-rowed perforation zones.
In both cases the beam originating from a laser light source is divided into two partial beams by means of a beam splitter, namely a part-reflecting mirror, which partial beams are then directed towards the wrapping material or the finished cigarette, respectively, each by means of a focusing lens element. Thus, one focusing lens element is required for each partial beam.
Several beam splitters can be connected one after the other for the perforation of wrapping materials so that more than two perforation rows can be formed also. This is not easily possible with the perforation of finished cigarettes in the filter attachement machine, since the beam splitters with lenses require a relatively great deal of space and thus cannot be accommodated in a conventional production installation.